The present invention relates to a probe adapted to be used with a pulse oximeter which enables measurement of oxygen saturation of arterial blood (SpO2) while being attached to a finger of a hand or a toe of a foot of a subject.
For measurement of the oxygen saturation of arterial blood of a subject, there has hitherto been used a probe adapted to be used with a pulse oximeter. In the pulse oximeter, a light emitting element and a light receiving element, which pair up with each other, are disposed opposite each other with a piece of tissue of a living body interposed therebetween, and oxygen saturation of arterial blood is determined by measuring the intensity of the light having passed through the tissue of the living body.
A probe, which has hitherto been known as a probe for a pulse oximeter of this type, has housings to which, e.g., a light emitting element and a light receiving element are mounted so as to oppose each other, and the housings are opened and closed while being pivoted around a joint shaft in the manner of a clothespin (see U.S. Pat, No. 4,685,464). With a spring (a clip), the light emitting element and the light receiving element are impelled so as to come close to each other. This probe is used for fingers of a hand, and the housings are attached to the finger of the subject in a pinching manner. That is, the subject's finger is sandwiched between the housings.
However, the two mutually-opposing housings are actuated around the joint shaft to thus open, or close. Hence, when variations exist among individuals in terms of thickness or size, as in the case of a finger, difficulty is encountered in causing a single probe to conform to all subjects. The probe cannot be appropriately attached to a finger which is greater than a predetermined thickness, and encounters difficulties of being displaced from a measurement site or becoming readily detached from the same. Since the spring force used for opening and closing the housings is specified, pain is inflicted when the probe is continuously attached over a long period of time. For this reason, the probe is inconvenient for use in, e.g., screening inspection of SAS (Sleep Apnea Syndrome), which requires attachment of a probe overnight.
In contrast with the probe adapted to be used with a pulse oximeter of such a spring (clip) type, there is also proposed another probe (see U.S. Pat. No. 5,776,059). The probe comprises a first casing section having a light receiving element, and a second casing section having a light emitting element, the casing sections being connected so as to be V-shaped. An adhesive member is provided at least on an interior surface of the first casing section. A nail of a finger or a toe of the subject is sandwiched between the first and second casing sections, to thus measure oxygen saturation of arterial blood. In order to fix this probe to the measurement site of the subject, providing the adhesive member to the interior surface of the casing section is indispensable.
The thus-configured probe is configured such that the first and second casing sections are connected so as to possess some degree of resilience. However, in order to cause the probe to be appropriately fixed to all fingers or the like, which vary in thickness or size among individuals, providing the adhesive member is indispensable. When dust, or the like, adheres to the adhesive member and this probe is reused, the accuracy of measurement is adversely affected, and a problem of sanitary administration is also raised.
Moreover, a disposable probe of an adhesive sheet structure has also been proposed as a probe which differs from the above-described probes in terms of structure (see Japanese Utility Model No. 2547840). However, when screening inspection of SAS is performed at home, the subject must wear this probe by himself/herself. In such a case, no limitations are imposed on a location where the probe is to be attached. However, attaching the probe to an appropriate measurement site requires knowledge or a technique. Further, the subject encounters difficulty in attaching the probe by himself or herself.
As mentioned previously, a required technique is required when the probe for a pulse oximeter is appropriately attached to a measurement site, and difficulty is encountered in the subject wearing the probe. Further, when the subject has attached the probe by himself/herself, the quality of measurement is often dependent on the state of attachment. For this reason, in order to accurately measure oxygen saturation of arterial blood, operation performed by a specialized engineer or by nursing personnel is required. There may be a case where long-duration attachment of the probe results in an increase in a sense of discomfort created by the living tissue in the measurement site, so that the subject takes the probe off consciously or subconsciously the probe for reasons of aches. Attaching the probe over a long period of time results in an increase in the chance of occurrence of a pressure mark, caused by localized pressure of the measurement site, and occurrence of blisters. Hence, the point where the probe is to be attached needs to be changed frequently, which in turn results in an increase in the burden imposed on the operator who performs measurement.